It sounds like exciting science: the hunt for the genes that make us human. But are we learning all that much about our biology by tracking down those parts of our genome that are unique to us?
In my Pacific Standard column this week, I argue no – at least not yet. The search for human specific genes, or those parts of our genome that show signs of rapid evolution, called “human accelerated regions” hasn’t really yielded much insight into what makes us different from other species, particularly our closest relatives. For the most part, we’ve discovered genes and regulatory elements that are somehow associated with brain function, but we can’t say much more than that.
The recent paper that describes a unique human genes that thickens the mouse neocortex is a great example. It’s a nice paper, and the result is tantalizing: you express a particular human gene in a mouse, and that causes a key population of neural progenitor cells to keep multiplying, resulting in a mouse with a bigger neocortex. But this study and other like it reveal little beyond a few molecular details. They don’t answer the question we really want to answer – why can we do algebra and chimps can’t? A learning a few molecular details about a few hundred or a few thousand human-specific/accelerated elements is unlikely to tell us much about that.
Not that we shouldn’t study these genes – it’s a necessary first step, and, more practically, they turn out to often be associated with psychiatric disorders. But we shouldn’t expect to learn too much about our unique human traits yet.